diff --git a/nvm.sh b/nvm.sh
index 3b618f1..37a5a6f 100644
--- a/nvm.sh
+++ b/nvm.sh
@@ -2110,14 +2110,14 @@ nvm_die_on_prefix() {
 
   for npmrc in $npmrcs; do
     if [ -f "${npmrc}/.npmrc" ]; then
-      NVM_NPM_PREFIX=$(grep ^prefix= ${npmrc}/.npmrc | sed s/prefix=\\\(.*\\\)$/\\1/)
-      if ! [ -z $NVM_NPM_PREFIX ]; then
+      NVM_NPM_PREFIX=$(grep ^prefix= "${npmrc}"/.npmrc | sed s/prefix=\\\(.*\\\)$/\\1/)
+      if ! [ -z "$NVM_NPM_PREFIX" ]; then
         break
       fi
     fi
   done
 
-  if ! [ -z $NVM_NPM_PREFIX ]; then
+  if ! [ -z "$NVM_NPM_PREFIX" ]; then
     if ! (nvm_tree_contains_path "$NVM_DIR" "$NVM_NPM_PREFIX" >/dev/null 2>&1); then
       if [ "_$NVM_DELETE_PREFIX" = "_1" ]; then
         npm config --loglevel=warn delete prefix